A process of preparing an unsaturated fatty acid through an unsaturated aldehyde from an olefin is a typical catalytic vapor phase oxidation process. Representative partial oxidation reactions of olefins include: a process of preparing (meth)acrylic acid through (meth)acrolein by the oxidation of propylene or isobutylene; a process of preparing phthalic anhydride by the oxidation of naphthalene or ortho-xylene; and a process of preparing maleic anhydride by the partial oxidation of benzene, butylenes, or butadiene. Among them, (meth)acrylic acid is being applied in various fields such as paints, textile auxiliary agents, coating agents, super absorbent polymers, etc., and thus, demand for high purity (meth)acrylic acid is rapidly increasing.
In general, a metal oxide catalyst used in the oxidation is prepared by a coprecipitation method, a hydrothermal method, sol gel synthesis, physical mixing, etc. In the process of preparing a metal oxide catalyst, a metal precursor is precipitated in the form of a polyanion, a metal oxide, or a metal hydroxide, and the physical properties and morphology of the precipitate vary according to the pH, concentration, reaction time, and aging time of the aqueous solution, and influences the physical state, particle size, and crystal structure of the catalyst.
In Patent Document 1, a technology for preparing a catalyst by coating a powder on a bulk carrier and firing is disclosed. This technology is characterized in that a catalyst drying temperature is 300° C., and a weight reduction rate of a dried material is 5˜40 mass %, but such a preparation method causes change in the catalyst structure due to a comparatively high drying temperature, thus deteriorating an unsaturated aldehyde conversion rate and selectivity. Thus, there is an urgent need for studies on a synthesis method that is capable of realizing an excellent unsaturated aldehyde conversion rate and selectivity, and easily providing a catalyst.